Sylvie Oddou-Muratorio, Cathleen Petit-Cailleux, Valentin Journé, Matthieu Lingrand, Jean-André Magdalou, Christophe Hurson, Joseph Garrigue, Hendrik Davi, Elodie Magnanou.Please use the format "First name initials family name" as in "Marie S. Curie, Niels H. D. Bohr, Albert Einstein, John R. R. Tolkien, Donna T. Strickland"
<p>1. Although droughts and heatwaves have been associated to increased crown defoliation, decreased growth and a higher risk of mortality in many forest tree species, their impact on tree reproduction and forest regeneration still remains understudied. Flowering, pollination and seed maturation processes are expected to be affected by prolonged water stress, eventually resulting in reproduction failure. However, inter-individual variations in growth and reproduction responses to drought-induced dieback could favor long-term adaptation at population level. 2. We investigated the relationships between individual crown defoliation, wood growth and reproduction in a drought-prone population of European beech, Fagus sylvatica. We used a spatially explicit mating model and marker-based parentage analyses to estimate effective female and male fecundities of 432 reproductive trees, which were also monitored for radial growth and crown defoliation over nine years. 3. Female and male fecundities markedly varied among individuals, more than did growth. Both female fecundity and growth decreased with increasing crown defoliation and competition and increased with size. Male fecundity only responded to competition, and tended to decrease with increasing competition. On average, the decline in female fecundity with increasing defoliation was nearly twice less strong as that of growth. Moreover, the negative effect of defoliation on female fecundity was size-dependent, with a slower decline in female fecundity with increasing defoliation for the large individuals. Finally, a tradeoff between growth and female fecundity was observed in response to defoliation, suggesting that some defoliated individuals can maintain significant female fecundity at the expense of reduced growth. 4. Synthesis. Our results suggest that while decreasing their growth, the large defoliated trees still contribute to reproduction through pollination and seed production. This non-coordinated decline of growth and fecundity at individual-level in response to water stress could compromise the evolution of drought-resistance traits at population level, and increase forest tree vulnerability.</p>
Crown defoliation, dieback, female fecundity, male fecundity, radial growth, Fagus sylvatica, Mixed Effect Mating Model, vulnerability, water stress
Climate change, Eco-evolutionary dynamics, Molecular ecology, Physiology, Population ecology
